Mechanical processing of high aspect ratio metallic tubing and related technology

ABSTRACT

Tubes for use in ultrahigh pressure devices, and associated systems and methods of manufacture are disclosed herein. In one embodiment, a metal tube includes an elongate bore having a circular transverse cross-sectional shape. The metal tube also includes an elongate wall extending around the bore and having an annular transverse cross-sectional shape with an inner surface closest to the bore, an outer surface furthest from the bore, and a wall thickness extending from the inner surface to the outer surface. An inner portion of the wall is under swage-autofrettage-induced overall compressive stress.

CROSS-REFERENCE TO RELATED APPLICATIONS INCORPORATED BY REFERENCE

The present application is a continuation of U.S. application Ser. No.15/462,733 filed Mar. 17, 2017, now U.S. Pat. No. 9,976,675, which is adivisional of U.S. application Ser. No. 14/924,591 filed Oct. 27, 2015,now U.S. Pat. No. 9,638,357, which is a divisional of U.S. applicationSer. No. 14/749,500, filed Jun. 24, 2015, and titled MECHANICALPROCESSING OF HIGH ASPECT RATIO METALLIC TUBING AND RELATED TECHNOLOGY,all of which are incorporated herein by reference in their entirety. Tothe extent the foregoing applications or any other material incorporatedherein by reference conflicts with the present disclosure, the presentdisclosure controls.

TECHNICAL FIELD

The present disclosure is directed generally to thick-walled tubing forcontaining and conveying ultrahigh pressure liquid, systems that includesuch tubing, and methods of manufacturing such tubing.

BACKGROUND

A variety of devices utilize ultrahigh pressure tubing, fittings, and/orother components that must withstand extreme pressures. In waterjetsystems, for example, liquid is often contained and directed throughtubes at ultrahigh pressures (i.e., pressures in excess of 30,000 psi).At pressures of this magnitude, high stresses are developed within thetubes. Repeated application of these pressures can lead to metal fatigueand eventual mechanical failure of the tubes. For example, repeatedpressurization cycles in a waterjet system can eventually initiatecracks at an inner wall of a tube along a plane of highest shear stress.This is known as stage I of the fatigue crack propagation process. Therepeated pressurization cycles can subsequently propagate the cracksfrom the inner wall towards an outer wall of the tube perpendicular tothe maximum applied alternating loads. This is known as stage II offatigue crack propagation. As the pressurization cycles continue thecrack can grow until the stress intensity at the crack tip reaches thefracture toughness of the material and the crack grows in an unstablefashion until through-wall failure takes place. This is known as stageIII of the fatigue crack propagation process. Tubing that is notregularly inspected and replaced to avoid failure due to the repeatedapplication of internal pressure loading can eventually suffer fatiguefailure. However, frequent inspection and replacement of tubes inwaterjet systems is expensive.

Currently, waterjet systems typically make use of stainless steel tubinghaving nominal outer diameters of ¼″, ⅜″, or 9/16″ and nominal insidediameters equal to approximately ⅓ of the outer diameter. Theseultrahigh pressure (UHP) stainless steel tubes typically have longlengths, and thereby have high aspect ratios (ratio of length to insidediameter). By virtue of their material and dimensions, UHP tubes canundergo numerous pressurization cycles before succumbing to fatiguefailure. Typical stainless steel UHP tubes used in waterjet systems, forexample, have operational lifespans of approximately 30,000pressurization cycles from atmospheric pressure to 60,000 psi.

In addition to selecting appropriate materials and dimensions for tubingused to contain and convey UHP liquid, certain manufacturing techniquescan be used to increase the operational lifespan of the tubing. Forexample, beneficial residual stresses can be induced within sections oftubing to increase the resistance to fatigue failure. In one method ofinducing beneficial residual stresses, tubes are subjected to aprocedure known as hydraulic autofrettage. This process involves thecontainment of a fluid within a tube and pressurization of the fluid toa pressure sufficient to produce a desired plastic deformation within aninner portion of a wall of the tube. The plastic deformation produces aslight increase in an inside diameter of the tube, and creates residualstresses in the wall of the tube.

Although the entire wall thickness is under hydraulic autofrettageinduced stresses, the innermost portion of the wall thickness is underthe greatest amount of induced beneficial compressive stress. Theresidual compressive stresses produced by the plastic deformationinclude radial and tangential stresses, the latter of which can beparticularly beneficial. The compressive stresses are at a maximum atthe inside diameter of the tube, and by reducing or minimizing themaximum shear stress from pressure cycles the compressive stresses candelay crack initiation and slow the growth of cracks. The benefit ofhydraulic autofrettage and the penetration depth of compressive stressesis dependent on the wall ratio of the tube (ratio of outside diameter toinside diameter), the tubing material strength, and the autofrettagepressure.

In addition to delayed stage I crack initiation, hydraulic autofrettagecan also slow stage II fatigue crack propagation by reducing the maximumprincipal stresses incurred during pressure cycles. Accordingly, byreducing the detrimental effects of pressurization cycles, hydraulicautofrettage can increase the fatigue life of the tubing and increasethe maximum allowable internal pressure a tube can withstand.

In the context of waterjet systems, hydraulic autofrettage can extendthe mean operational lifespan of tubing by 40 to 50%. For example,rather than 30,000 pressurization cycles from atmospheric pressure to60,000 psi, a waterjet system utilizing tubing that has undergonehydraulic autofrettage can often perform up to 45,000 of thesepressurization cycles. Although this increase in the operationallifespan of tubing is beneficial, additional increases in theoperational lifespan of tubing are desirable to provide additionaldecreases in maintenance and operational costs of waterjet systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a partially schematic, isometric and cross-sectional view ofa prior art tube prior to undergoing hydraulic autofrettage.

FIG. 1B is a partially schematic, isometric and cross-sectional view ofthe prior art tube of FIG. 1A, subsequent to undergoing hydraulicautofrettage.

FIG. 2A is a partially schematic, isometric and cross-sectional view ofa tube prior to undergoing swage autofrettage in accordance with anembodiment of the present disclosure.

FIG. 2B is a partially schematic, isometric and cross-sectional view ofthe tube of FIG. 2A, subsequent to undergoing swage autofrettage inaccordance with an embodiment of the disclosure.

FIG. 3 is a partially schematic, isometric view of a system configuredin accordance with an embodiment of the disclosure for producingultrahigh pressure tubes.

FIGS. 3A and 3B are detail views of portions of FIG. 3.

FIG. 4 is a partially schematic, isometric view of a system configuredin accordance with another embodiment of the disclosure for producingultrahigh pressure tubes.

FIGS. 4A and 4B are detail views of portions of FIG. 4.

FIG. 5 is a partially schematic, cross sectional view of a systemconfigured in accordance with yet another embodiment of the disclosurefor producing ultrahigh pressure tubes.

FIG. 6 is a flow diagram of a method for performing swage autofrettageof tubes in accordance with an embodiment of the disclosure.

FIG. 7 is a flow diagram of a method for performing swage autofrettageof tubes in accordance with another embodiment of the disclosure.

FIG. 8 is a flow diagram of a method for performing swage autofrettageof tubes in accordance with yet another embodiment of the disclosure.

FIG. 9 is a perspective view of a waterjet system having tubesconfigured in accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

The present technology is directed generally to components for use inultrahigh pressure devices, and more specifically to systems and methodsfor mechanical swage autofrettage and the components produced by suchsystems and methods. At least some embodiments of the present technologyinclude a metal thick-walled tube having an elongate bore and a circulartransverse cross-sectional shape. The metal tube includes an elongatewall extending around the bore and having an annular transversecross-sectional shape with an inner surface closest to the bore, anouter surface furthest from the bore, and a wall thickness extendingfrom the inner surface to the outer surface. An inner portion of thewall is under swage-autofrettage-induced overall compressive stress. Inother embodiments, the devices, systems and associated methods can havedifferent configurations, components, and/or procedures. Still otherembodiments may eliminate particular components and/or procedures. Aperson of ordinary skill in the relevant art, therefore, will understandthat the present technology, which includes associated devices, systems,and procedures, may include other embodiments with additional elementsor steps, and/or may include other embodiments without several of thefeatures or steps shown and described below with reference to FIGS. 1-9.

Certain details are set forth in the following description and FIGS. 1-9to provide a thorough understanding of various embodiments of thedisclosure. Other details describing well-known structures and systemsoften associated with high-pressure tubes and the components or devicesassociated with the manufacturing of high-pressure tubes, however, arenot set forth below to avoid unnecessarily obscuring the description ofthe various embodiments of the disclosure. Moreover, although severalembodiments disclosed herein are primarily or entirely directed towaterjet applications, other applications in addition to those disclosedherein are within the scope of the present technology. Furthermore,waterjet components or systems configured in accordance with embodimentsof the present technology can be used with a variety of suitable fluids,such as water, aqueous solutions, hydrocarbons, glycol, and liquidnitrogen, among others. As such, although the term “waterjet” is usedherein for ease of reference, unless the context clearly indicatesotherwise, the term refers to a jet formed by any suitable fluid, and isnot limited exclusively to water or aqueous solutions. Additionally, theterm “waterjet” can refer to a jet that includes abrasive particles,e.g., an abrasive waterjet.

Many of the details and features shown in the Figures are merelyillustrative of particular embodiments of the disclosure. Accordingly,other embodiments can have other details and features without departingfrom the spirit and scope of the present disclosure. In addition, thoseof ordinary skill in the art will understand that further embodimentscan be practiced without several of the details described below.Furthermore, various embodiments of the disclosure can includestructures other than those illustrated in the Figures and are expresslynot limited to the structures shown in the Figures. Moreover, thevarious elements and features illustrated in the Figures may not bedrawn to scale.

As discussed above, hydraulic autofrettage can produce relativelysignificant residual compressive stresses within the inner wall of thetubes and can increase the fatigue life of these components when theyare subsequently subjected to pressure cycles. In addition, thehydraulic autofrettage process can increase the maximum allowableinternal pressure a tube can withstand before additional yielding beginsto occur. As an alternative to hydraulic autofrettage, mechanical orswage autofrettage can be used to increase the fatigue life and/or theelastic pressure rating of components subjected to high pressures. Forexample, swage autofrettage may be used to improve the fatigue life oflarge caliber artillery gun barrels. During swage autofrettage of abarrel, a mandrel having a diameter slightly larger than the barrel'sbore can be directed through the bore. The passage of the mandrelenlarges the bore, producing plastic deformation in the metal adjacentto the bore. Similar to hydraulic autofrettage, the plastic deformationfrom swage autofrettage creates high compressive stresses at theinnermost section of the barrel that can inhibit fatigue cracknucleation and slow crack growth by reducing or minimizing the maximumshear stress developed during subsequent pressure cycles. Thecompressive stresses reduce the detrimental effects of pressurizationcycles and increase the fatigue life of the barrel. Similar to thehydraulic autofrettage process, the swage autofrettage process can alsoincrease the maximum allowable internal pressure the barrel canwithstand (elastic strength) before additional yielding begins to occursubsequent to the process. For both the hydraulic autofrettage processand the swage autofrettage process, residual stresses must resolvethemselves within the part so that equilibrium conditions are satisfied.

Importantly, compared to hydraulically autofrettaged tubes, themagnitude of compressive stresses can be greater in swage autofrettagedtubes. Additionally, the swaging process can induce axial compressivestresses when the mandrel is progressed through the tube. The benefit ofswage autofrettage can be dependent on the wall ratio of the tube, thematerial, and the mandrel shape & diameter. Importantly, the fatiguelife of swage autofrettaged components can be far greater thanhydraulically autofrettaged components for a given overstrain.

Swage autofrettage, while advantageous for the reasons stated above, hasnot been recognized as an option for autofrettage of high aspect ratiotubes (tubes having a high ratio of length to inside diameter). Forexample, swage autofrettage in the context of gun barrels and other lowaspect ratio tubes requires the use of pushrods or pull-rods to forcemandrels through the barrels. When performing swage autofrettage on highaspect ratio tubing using conventional techniques, the pushrods orpull-rods would be susceptible to bending, buckling or breakage, whichwould interrupt the autofrettage process and/or damage the componentsbeing subjected to the process. Breakage of pushrods or pullrods canrequire expensive repairs or replacement. In view of thesecomplications, swage autofrettage is not conventionally used on highaspect ratio tubes, such as those used in waterjet systems. In contrast,hydraulic autofrettage does not require a pushrod or a pullrod, and itcan generally be employed on much longer components than swageautofrettage. Even so, hydraulic autofrettage can be slow, complex,expensive and dangerous.

Although counterintuitive for use on the high aspect ratio tubing usedin waterjet systems, the inventors have discovered methods to reliablyconduct swage autofrettage on such tubes. Moreover, the inventors havediscovered systems and methods that reduce or eliminate at least some ofthe challenges conventionally thought to make the swage autofrettageprocess unsuitable for the production of tubing for waterjet systems.These and other features of at least some embodiments of the presentdisclosure are described below.

FIG. 1A is a partially schematic, isometric and cross-sectional view ofa prior art tube 100 prior to undergoing hydraulic autofrettage. Thetube 100 has a circular transverse cross-sectional shape and includes anelongate cylindrical wall 102 defining a longitudinal bore 104 andhaving a first inside diameter 106 a. The wall 102 has an annulartransverse cross-sectional shape and extends from an inner surface 103to an outer surface 105. The wall 102 is formed from a metal or metalalloy, typically an austenitic stainless steel, containing a pluralityof relatively evenly distributed crystalline grains intermixed withprecipitates 108 within the wall 102. FIG. 1B is a partially schematic,isometric and cross-sectional view of the prior art tube 100 subsequentto undergoing hydraulic autofrettage. When performing hydraulicautofrettage, the entire length of the tube being processed is subjectedto internal pressure. Comparing FIG. 1B to FIG. 1A, the hydraulicautofrettage process has enlarged the bore 104 via hydraulicautofrettage compression of the wall 102 in a first portion 110 that isadjacent to the bore 104. Specifically, the compression of the wall 102produces a second inside diameter 106 b that is larger than the firstinside diameter 106 a. Hence, after the hydraulic autofrettage, the bore104 has a greater transverse cross-sectional area.

The compression of the wall 102 produces compressive stresses within thefirst portion 110. The compressive stresses include stresses in a radialdirection R and in a tangential direction T. A second portion 112 of thewall 102 further from the inner surface 103 than the first portion 110is in a state of residual tangential tension and a small degree ofradial compression; and the radial stresses at the bore and outsidediameter are zero. The extent of the compression of the wall thatproduces the compressed first portion 110 is dependent upon the materialstrength of the tube 100, the wall ratio of the tube 100 (ratio ofoutside diameter to inside diameter), and the hydraulic pressure that isexerted on a fluid within the bore during the hydraulic autofrettageprocess. The greater the pressure, the greater the extent of thecompressed first portion 110. Notably, in the context of hydraulicautofrettage, over-pressurization can potentially result in a rupture ofthe tube 100. Accordingly, the pressure is carefully managed duringhydraulic autofrettage such that the maximum tangential compressivestresses are attained in the first portion 110 of the wall 102 along aradial line from the inner surface 103 to the side surface or outersurface 105.

FIG. 2A is a partially schematic, isometric and cross-sectional view ofa tube 200 prior to undergoing swage autofrettage in accordance with anembodiment of the present disclosure. In the illustrated embodiment, thetube 200 has a circular transverse cross-sectional shape and includes anelongate cylindrical wall 202 having an inner surface 203 and a sidesurface or outer surface 205. The wall 202 has an annular transversecross-sectional shape and defines a longitudinal bore 204 having aninitial or first inside diameter 206 a. Similar to the tube 100, thewall 202 is formed from a metal or metal alloy, most typically anaustenitic stainless steel containing a plurality of relatively evenlydistributed crystalline grains intermixed with precipitates 208 withinthe wall 202. The cross-sectional view of FIG. 2A illustrates only aportion of the entire length of the tube 200, and may not be drawn toscale. Accordingly, it is to be understood that the tube 200 can have asignificant length, as well as a variety of inside and outsidediameters. In at least some embodiments, the tube 200 has an aspectratio (ratio of length to inside diameter) of 90 or more and includes abore having a diameter of less than 0.25 inches. For example, the tubecan have an inner diameter of 0.2 inches and a length greater than threefeet. In other embodiments, the aspect ratio can be less than 90 and theinside diameter can be greater than 0.25 inches. Furthermore, in atleast some embodiments, the wall ratio (i.e., the ratio of the outsidediameter to the inside diameter) is between 2 and 5.

FIG. 2B is a partially schematic, isometric and cross-sectional view ofthe high aspect ratio tube 200 subsequent to undergoing swageautofrettage in accordance with an embodiment of the disclosure.Comparing FIG. 2B to FIG. 2A, the swage autofrettage has enlarged thebore 204 via compression of the wall 202 in a first portion 210 that isadjacent to the bore 204. Similar to the hydraulic autofrettage processdiscussed above, the compression of the wall 202 produces a subsequentor second inside diameter 206 b that is larger than the first insidediameter 206 a, and the swage autofrettage thereby increases thetransverse cross-sectional area of the bore 204. Notably, however, thecompression of the wall 202 via swage autofrettage produces greatercompressive stresses within the wall 202 than the compressive stressesproduced in the wall 102 via the hydraulic autofrettage of the tube 100.In particular, given the same degree of overstrain as hydraulicautofrettage, the swage autofrettaged tube 200 illustrated in FIG. 2Bexhibits greater overall compressive stresses within the first portion210 of the wall 202. Additionally, in the case of swage autofrettage,the overstrain creates the residual stresses within the tube as themandrel passes through the bore as opposed to the entire tube beingsubjected to the internal pressure and overstrain when the pressure isapplied via hydraulic autofrettage.

The compression of the wall 202 produces compressive stresses within thefirst portion 210 in a radial direction R and a tangential direction T.In contrast to the hydraulic autofrettage described above, the swageautofrettage also produces compressive stresses in the first portion 210in an axial direction A. A second portion 212 of the wall 202 furtherfrom the inner surface 203 than the first portion 210 is in a state ofresidual tangential and axial tension and a small degree of radialcompression; and the radial stresses at the bore and outside diameterare at zero.

Without being bound by any theory or mechanism, it is believed thatswage autofrettage produces compressive stresses in the axial directionvia displacement and/or dislocation of the metal microstructures 208 inthe axial direction. These additional compressive stresses providefurther elastic strengthening of the tube 200. Utilizing the systems andmethods disclosed herein, the inventors have produced UHP stainlesssteel tubes that can withstand 175,000 pressurization cycles ofatmospheric pressure to 60,000 psi. The baseline fatigue data forunprocessed tubing of the same material is 30,000 cycles, andhydraulically autofrettaged tubing fatigue life is 42,600 pressurecycles. Therefore, the swage autofrettage process disclosed hereinsurprisingly provides a fatigue life that is 480% greater than that ofan unprocessed tube, and 310% greater than that of a hydraulicallyautofrettaged tube.

Embodiments configured in accordance with the present technology caninclude tubes and mandrels having a variety of dimensions. In oneembodiment, the tube 200 has a length of 20 feet, a first insidediameter 206 a of 0.125 inches, and a wall thickness of 0.125 inches.The dimensions and the material of the tube 200 can provide lateralflexibility. For example, in several embodiments, the tube 200 can belaterally flexible such that it can be laterally displaced at a midpointof its length by a distance equal to 10% of its length withoutundergoing permanent deformation. In several embodiments, the mandrelcan have a diameter that is approximately 3-4% larger than the firstinside diameter 206 a, resulting in a second inside diameter 206 b of0.1275 inches to 0.1283 inches. In other embodiments, the tube 200 canhave smaller or larger first diameters 206 a, second diameters 206 b,and/or wall thicknesses. Moreover, the outside diameter and/or the wallratio can be uniform or mostly uniform throughout the length of the tube200. For example, in some embodiments the wall ratio does not deviate bymore than 15% throughout the length of the tube 200.

Additionally, in several embodiments, multiple mandrels may be used insuccession to perform swage autofrettage. For example, a first mandrelwith a diameter 1% larger than the first inside diameter 206 a may bedirected through the tube 200, and subsequent mandrels, each with adiameter 1% larger than the preceding mandrel, may subsequently bedirected through the tube 200. In such embodiments, one or more mandrelsmay be used to expand the bore of the tube 200 to correspondingintermediate inside diameters. Subsequently, a final mandrel can be usedto expand the bore to a final inside diameter.

Several embodiments configured in accordance with the present technologycan include mandrels having diameters that are less than 1% greater thanthe first diameter 206 a or more than 4% greater than the first diameter206 a. For example, in some embodiments, a mandrel having a maximumoutside diameter that is approximately equal to the inside diameter ofthe tube (e.g., less than 0.25% larger) may be used to clean the innersurface of the tube 200.

FIG. 3 is a partially schematic, isometric view of a system 300configured in accordance with an embodiment of the disclosure forproducing ultrahigh pressure tubes. FIGS. 3A and 3B are detail views ofportions of FIG. 3. Referring to FIGS. 3, 3A and 3B, together, thesystem 300 includes a first gripper 316 and a second gripper 302. Thefirst gripper 316 can be fixedly attached to the second gripper 302 tosecure the tube 200 in a fixed position with respect to the secondgripper 302. Specifically, the first gripper 316 includes a firstgripping surface 317 (FIG. 3A) that can contact the side surface 205 ofthe tube 200 to releasably secure the tube 200. Although shownschematically in the illustrated embodiment, the first gripper 316 canbe a hydraulically operated gripping mechanism. In some embodiments, thefirst gripper 316 can be operated via other automatic methods (e.g.,pneumatic, electromechanical, etc.), or it can be manually operated(e.g., via gears, threads or other mechanical components).

The second gripper 302 includes a base 304, a first track assembly 306 aand a second track assembly 306 b (collectively the track assemblies306). The track assemblies 306 are operably coupled to the base 304 viaa press 308 and drive motors 310. The press 308 can include gears orhydraulic components that can move one or both of the track assemblies306 along a vertical axis V. In particular, the press 308 can move thetrack assemblies 306 towards or away from one another to vary a distanceD between the track assemblies 306. Additionally, the press 308 canapply significant forces on a pushrod 311 or other object positionedbetween the track assemblies 306.

The track assemblies 306 include treads 312 that are operably coupled tothe drive motors 310 via an internal drive mechanism (not visible inFIG. 3), and the drive motors 310 can drive the treads 312 in rotatingloops. For example, the tread 312 on the first track assembly 306 a canbe driven to rotate in a counter-clockwise direction, while the tread312 on the second track assembly 306 b can be driven to rotate in aclockwise direction. The treads or belts 312 include a second grippingsurface 313 (FIG. 3B) on an outwardly facing surface that can contact aside surface 315 of the pushrod 311. Although the illustrated embodimentof FIG. 3 includes the treads 312, in other embodiments the trackassemblies 306 may include belts, tracks and/or other components thatcan be driven to rotate. As described further below, the rotating treads312 can drive the pushrod 311 (or another component) laterally throughthe second gripper 302. The system 300 also includes a plurality ofstands 318 and a guide 314. The stands 318 can support the tube 200 andthe guide 314 can align and guide the pushrod 311.

The system 300 can include a control portion 322 having a controller 324and a control panel 326. The controller 324 can be operably coupled to apower source via, e.g., a power cord 329. The control portion 322 caninclude a variety of electrical, mechanical and/or electromechanicalcomponents, and these components can be used to operate the secondgripper 302 and the first gripper 316. For example, the control portion322 and/or the controller 324 can include one or more programmable logiccontrollers (PLCs) 323, relays 325, integrated circuits 330, processors331 and computer readable media or memory 333 (e.g., flash memory, solidstate drives, hard drives, other types of ROM or RAM, etc.). The memory333 can contain software or computer code for operation of the system300. The control portion 322 can also include a hydraulic system 327that is operably coupled to the press 308, the first gripper 316 and thecontroller 324. The hydraulic system 327 can include a pump 332 andcontrol lines 334. The controller 324 can control operation of the pump332 to provide pressurized hydraulic fluid to the press 308 and to thefirst gripper 316 via the control lines 334. Additionally, thecontroller 324 can be electrically coupled to the drive motors 310 toprovide signals for operation of the track assemblies 306.

In operation, the system 300 can perform swage autofrettage on tubes orother components, including tubes having relatively long lengths. Forexample, the tube 200 can be placed on the stands 318 with an end of thetube 200 positioned at least partially within the first gripper 316. Anoperator can subsequently operate the control panel 326 to actuate thefirst gripper 316 and releasably secure the tube 200 relative to thesecond gripper 302. A mandrel 336 having a maximum diameter that isgreater than or equal to the first diameter 206 a can be positioned atleast partially within the bore of the tube 200 and proximate to thefirst gripper 316. The pushrod 311 can be positioned on the first trackassembly 306 a and aligned with the mandrel 336 and the bore. Theoperator can then actuate the press 308 via the control panel 326 tomove the second track assembly 306 b toward the first track assembly 306a to operably engage the pushrod 311 between the track assemblies 306.For ease of illustration, the mandrel 336 and other components have notbeen drawn to scale. Specifically, in the illustrated embodiment of FIG.3 (and in several subsequent Figures), the mandrel 336 is drawn largerto more clearly illustrate the positioning and/or features of themandrel 336. In some embodiments, the mandrel 336 can have a diameterthat is 2% greater than the inside diameter of the tube 200. In otherembodiments, the mandrel 336 can have other dimensions.

With the tube 200 secured by the first gripper 316, the operator canactuate one or both of the track assemblies 306. That is, the operatorcan drive the first track assembly 306 a and/or the second trackassembly 306 b to rotate one or both of the treads 312. The treads 312advance the second gripping surface 313 along a longitudinal axis L andin a direction D_(L) toward the tube 200. The gripping surface 313 actson the side surface 315 of the pushrod 311 to drive the pushrod 311 inthe direction D_(L) such that a distal end 337 of the pushrod 311 exertssignificant force on the mandrel 336 and forces the mandrel 336 into thebore. As the track assemblies 306 continue to rotate the treads 312, themandrel 336 is driven distally (i.e., away from the track assemblies)and further into the tube 200, and the pushrod 311 enters the bore.

In several embodiments, the pushrod 311 can have a diameter that issimilar to the inside diameter of the tube 200. For example, the pushrod311 can have a diameter that is larger than the inside diameter of thetube 200 prior to swage autofrettage, but slightly smaller than theinside diameter of the tube 200 after swage autofrettage. Hence, thepushrod 311 can fit nearly flush within the bore of the tube 200, andthe wall of the tube 200 can at least partially support the pushrod 311as the distal end 337 is pushed into and through the bore. The supportprovided by the tube 200 can reduce the likelihood of damage to thepushrod 311. For example, absent the relatively tight fit of the pushrod311 within the bore, the pushrod 311 can be susceptible to bending orbuckling from the force required to push the mandrel 336 through thetube 200. Nevertheless, in some embodiments, the pushrod 311 can have asmaller diameter, including a diameter smaller than the inside diameterof the tube 200 prior to swage autofrettage. Even in embodiments havingsmaller diameter pushrods, the tube 200 can provide support for thepushrod during swage autofrettage via the system 300. Notably, thepushrod 311 can have a length that is longer than the tube 200, and asthe distal end 337 of the pushrod is driven through the tube 200, thetube 200 can provide support for each incremental portion of the pushrod311 that enters the tube 200.

A variety of additional steps or procedures can be included in the swageautofrettage process described above with respect to the system 300. Forexample, in several embodiments, preparation of the tube 200 can beincluded as part of the swage autofrettage process. In severalembodiments, a cone can be formed in the bore of the tube 200 to receivethe mandrel 336. The cone can extend at least partially into the bore toreceive and support at least a portion of the mandrel 336 prior to themandrel being pushed through the bore. The cone can be formed in thetube 200 via a variety of suitable machine tools (e.g., boring via arouter or drill). After the formation of the cone, the tube 200 can becleaned prior to inserting the mandrel in the bore. Additionally,lubricant(s) (e.g., mandrelizing grease) can be used to facilitate thepassage of the mandrel 336 through the bore during the swageautofrettage process.

In the illustrated embodiment of FIG. 3, the first track assembly 306 aand the second track assembly 306 b are both coupled to the press 308.In other embodiments, only one of the track assemblies 306 may becoupled to the press 308. For example, the first track assembly 306 amay be operably coupled to one of the drive motors 310 and fixedlyattached to the base 304 via a mount (not shown).

The systems and methods described herein can be tailored to provide adesired increase in fatigue life and/or a desired increase in elasticstrength. In several embodiments, the primary objective is to increasefatigue life. In such embodiments, the size of the mandrel 336, thespeed of the gripping surface 313, and/or other factors can be used tosubject the tube 200 to a desired pressure or overstrain during theautofrettage process. The desired pressure can be selected to reduce themaximum shear stresses per the Tresca criterion. In other embodiments,similar factors may be selected to produce a higher pressure oroverstrain and provide greater elastic strength subsequent to theautofrettage process. The desired pressure or overstrain generatedduring the autofrettage process can be dependent upon the operatingpressure that the tube will be subjected to, the wall ratio of the tube,and the yield strength of the material.

FIG. 4 is a partially schematic, isometric view of a system 400configured in accordance with an embodiment of the disclosure forproducing ultrahigh pressure tubes. FIGS. 4A and 4B are detail views ofportions of FIG. 4. Similar to the system 300, the system 400 includes afirst gripper 416 and a second gripper 402 having a base 404. Referringto FIGS. 4, 4A and 4B, together, the first gripper 416 includes a firstgripping surface 417 (FIG. 4A) that can contact the side surface 205 ofthe tube 200 to releasably secure the tube 200. The second gripper 402includes a first plurality of rollers or first set of rollers 406 a anda second plurality of rollers or second set of rollers 406 b(collectively the rollers 406 or sets of rollers 406). The rollers 406are operably coupled to the base 404 via a press 408 and drive motors410. The rollers 406 include a second gripping surface 407 on anoutwardly facing surface of the rollers 406. The press 408 can besubstantially similar to the press 308, and can include gears orhydraulic components that can move one or both sets of rollers 406 alonga vertical axis V. In particular, the press 408 can move the sets ofrollers 406 towards or away from one another to vary a distance Dbetween the sets of rollers 406. The press 408 can also applysignificant forces on the pushrod 311 or other object positioned betweenthe rollers 406.

The rollers 406 can be made from metal or metal alloys (e.g., steel), orfrom a variety of other materials. In several embodiments, the secondgripping surface 407 is shaped to align with the pushrod 311. Forexample, in one embodiment, the second gripping surface 407 can beconcave and can include a radius of curvature that is shaped to beslightly larger than the radius of the pushrod 311. In otherembodiments, the curvature can be equal to or less than the radius ofcurvature of the pushrod 311. Shaping the second gripping surface 407 toalign with the pushrod 311 can reduce the possibility of slippage whenthe pushrod 311 is driven by the rollers 406 (as described furtherbelow), and it can help to maintain the pushrod 311 in alignment withthe tube 200.

The rollers 406 can be operably coupled to the drive motors 410 via aninternal drive mechanism (e.g., one or more gears, sprockets, chains orother drive components), and the drive motors 410 can rotate the rollers406. For example, the first set of rollers 406 a can be rotated in acounter-clockwise direction, while the second set of rollers 406 b canbe rotated in a clockwise direction. As described further below, therotating rollers 406 can drive the pushrod 311 (or another component)along a longitudinal axis L through the second gripper 402.

The system 400 can include several additional components that aresubstantially similar to the components of the system 300. For example,the system 400 can include a guide 414, a plurality of stands 418, acontrol portion 422, a controller 424, a control panel 426 and a powercord 429. Additionally, the control portion 422 and/or the controller424 can include Programmable Logic Controller(s) (PLC) 423, relays 425,integrated circuits 430, processors 431 and computer readable media ormemory 433; and the control portion 422 can also include a hydraulicsystem 427 having a pump 432 and control lines 434.

In operation, the system 400 can perform swage autofrettage in a mannersimilar to the system 300. For example, the tube 200 can be placed onthe stands 418 and secured via the first gripper 416. The pushrod 311can be positioned on the first set of rollers 406 and aligned with themandrel 336 and the bore. The operator can actuate the press 408, engagethe pushrod 311 between the rollers 406, and then actuate rotation ofthe rollers 406 to move at least a portion of the second grippingsurface 407 in a direction D_(L) toward the tube 200. Movement of thesecond gripping surface 407 toward the tube 200 drives the pushrod 311toward the tube 200, forcing the mandrel 336 into and through the tube200.

FIG. 5 is a partially schematic, cross sectional view of a system 500configured in accordance with an embodiment of the disclosure forproducing ultrahigh pressure tubes. In the illustrated embodiment, thesystem 500 includes a pusher 502 mounted to a base 504. The pusher 502can be hydraulically actuated and include a double acting, hollowplunger cylinder 503. In some embodiments, the pusher 502 can be ahollow plunger cylinder manufactured by Enerpac, of Menomonee Falls,Wis., and having a model number of RRH-307. As described in more detailbelow, the pusher 502 can push or advance the pushrod 311 to drive themandrel 336 through the tube 200. Several components in FIG. 5 are notdrawn to scale. For example, the dimensions of the mandrel 336 and thetube 200 are exaggerated to better illustrate swage autofrettage via thesystem 500. Specifically, the diameter of the mandrel 336 is shown assignificantly larger than the inside diameter of the tube 200 to betterillustrate the swage autofrettage process. In several embodiments, themandrel 336 includes a diameter that is closer to that of the insidediameter of the tube, and the deformation of the tube is significantlyless than that shown in FIG. 5.

The system 500 can also include a plurality of clamps or grippers 506(identified individually as a first gripper 506 a, a second gripper 506b and a third gripper 506 c). The clamps or grippers 506 can be similarto the first grippers 316 and 416 described above with respect to thesystems 300 and 400, and can be used to releasably secure the tube 200and the pushrod 311. The term “gripper,” as used herein, can refer toany device, system, component or assembly that contacts a tube or apushrod to secure or advance the tube or pushrod. For example, the termgripper can refer to the first grippers 316 and 416, the second grippers302 and 402, the track assemblies 306, the treads 312, the rollers 406,the pusher 502 and/or the clamps or grippers 506.

The first gripper 506 a includes a first gripping surface 509 a, thesecond gripper 506 b includes a second gripping surface 509 b, and thethird gripper 506 c includes a third gripping surface 509 c. The firstgripper 506 a and the third gripper 506 c are operably coupled to thebase 504, and the second gripper 506 b is slidably coupled to the base504. Although not shown in FIG. 5, the system 500 can include a controlportion and associated components to operate the pusher 502 and thegrippers 506. For example, the system 500 can include a hydraulic pump,control lines, a controller, a control panel, PLCs, relays, processors,integrated circuits, memory, and/or other components to control theoperation of the pusher 502 and the grippers 506.

In operation, the system 500 can perform swage autofrettage on the tube200 via alternating activation of the grippers 506 and the pusher 502.For example, the first gripper 506 a can be activated to engage thefirst gripping surface 509 a with the side surface 205 of the tube 200to releasably secure the tube 200. The second gripper 506 b can beactivated to engage the second gripping surface 509 b with the sidesurface 315 of the pushrod 311 to slidably secure the pushrod 311.Subsequently, pressurized hydraulic fluid can be directed to the pusher502 to drive the hollow cylinder 503 against the second gripper 506 b.The force from the cylinder 503 drives the second gripper 506 b and thesecond gripping surface 509 b in a direction D_(L) along a longitudinalaxis L and toward the tube 200. The second gripping surface 509 b drivesthe pushrod 311 in the direction DL, forcing the mandrel 336 into thetube 200. The hydraulic fluid continues to drive the cylinder 503 towardthe tube 200 until the cylinder reaches the end of its stroke. The thirdgripper 506 c is then activated to engage the third gripping surface 509c with the side surface 315 of the pushrod 311 to secure the pushrod311; and the second gripper 506 b is deactivated or released. Thecylinder 503 and the second gripper 506 b are returned to their initialposition at the back of the stroke, and the second gripper 506 b is thenreactivated to secure the pushrod 311. In some embodiments, the secondgripper 506 b can be returned to the initial position via a spring orother automatic return mechanism. With the second gripper 506 b in itsinitial position and securing the pushrod 311, the third gripper 506 cis deactivated. Hydraulic fluid is then directed to the pusher 502 toinitiate another stroke of the cylinder 503 and force the mandrel 336further into the tube 200. This process is then repeated until themandrel is driven through the tube 200.

The systems 300, 400 and 500 can perform swage autofrettage to enhancethe fatigue resistance of tubes via a variety of methods. FIG. 6 is aflow diagram of a method 600 for performing swage autofrettage of thetube 200 via the system 300 and in accordance with an embodiment of thedisclosure. The method 600 begins at step 602, where the tube 200 isprepared for swage autofrettage. The tube preparation can includeformation of a cone in the bore, cleaning of the tube 200, and theapplication of mandrelizing grease to the bore of the tube 200. At step604, the tube 200 is placed on the stands 318 and secured via the firstgripper 316. At step 606, the mandrel 336 is positioned at leastpartially within the bore of the tube 200 (e.g., at least partiallywithin a cone formed in the bore). At step 608, the pushrod 311 ispositioned to extend through the guide 314 and along the first trackassembly 306 a, abutting the mandrel 336. At step 610, the press 308 isactivated to move the second track assembly 306 b toward the first trackassembly 306 a and grip the pushrod 311 therebetween. At step 612, thetrack assemblies 306 are driven to rotate the treads 312 and advance thepushrod 311 against the mandrel 336, thereby advancing the mandrel 336longitudinally within the bore and forcing the mandrel 336 through thetube 200. After step 612, the method 600 concludes.

FIG. 7 is a flow diagram of a method 700 for performing swageautofrettage of the tube 200 via the system 400 and in accordance withan embodiment of the disclosure. The method 700 can include severalsteps that are at least similar to the method 600. For example, themethod 700 begins at step 702, where the tube 200 is prepared for swageautofrettage. Similar to step 602 of the method 600, the tubepreparation of step 702 can include formation of a cone in the bore,cleaning of the tube 200, and the application of mandrelizing grease tothe bore of the tube 200. At step 704, the tube 200 is placed on thestands 418 and secured via the first gripper 416. At step 706, themandrel 336 is positioned at least partially within the bore of the tube200. At step 708, the pushrod 311 is positioned to extend through theguide and between the rollers 406, abutting the mandrel 336. At step710, the press 408 is activated to grip the pushrod 311 between therollers 406. At step 712, the rollers 406 are driven to rotate andadvance the pushrod 311 against the mandrel 336, thereby advancing themandrel 336 longitudinally within the bore and forcing the mandrel 336through the tube 200. After step 712, the method 700 concludes.

FIG. 8 is a flow diagram of a method 800 for performing swageautofrettage of the tube 200 via the system 500 and in accordance withan embodiment of the disclosure. Method 800 begins at step 802, wherethe tube 200 is prepared for swage autofrettage. Similar to steps 602and 702, the tube preparation of step 802 can include formation of acone in the bore, cleaning of the tube 200, and the application ofmandrelizing grease to the bore of the tube 200. At step 804, the tube200 can be placed on stands and secured via the first gripper 506 a. Atstep 806, the mandrel 336 is positioned at least partially within thebore of the tube 200. At step 808, the pushrod 311 is positioned toextend through the third gripper 506 c, the pusher 502, and the secondgripper 506 b, abutting the mandrel 336. At step 810, the second gripper506 b is activated to grasp the pushrod 311. At step 812 the pusher isactivated to drive the cylinder 503 in the direction of the secondgripper 506 b, forcing the second gripper 506 b and the pushrod 311toward the tube 200 and driving the mandrel 336 further into the bore ofthe tube 200. At step 814, the third gripper 506 c is activated to graspthe pushrod 311, and the second gripper 506 b is released. At step 816,the cylinder 503 and the second gripper 506 b are returned to theirinitial position at the back of the stroke. At step 818, the secondgripper 506 b is activated, and the third gripper 506 c is released. Atstep 820, steps 812 through 818 are repeated until the mandrel 336 ispushed out the end of the tube 200. After step 820, the method 800concludes.

In addition to the methods 600, 700 and 800 for performing swageautofrettage, the disclosed technology includes a variety of othermethods for performing swage autofrettage. For example, the systems 300,400 and 500 can be used to secure a pushrod while a tube is advancedover a mandrel positioned at the end of the pushrod. In one method, thepushrod 311 is positioned on the stands 318 and secured via the firstgripper 316. The tube 200 is positioned to extend through the guide 314and along the first track assembly 306 a. The press 308 is thenactivated to move the second track assembly 306 b toward the first trackassembly 306 a and grip the tube 200 therebetween. The mandrel 336 canbe positioned at least partially within the tube 200 and adjacent thepushrod 311. The track assemblies 306 are then driven to rotate thetreads 312 and advance the tube 200 toward the pushrod 311, therebyadvancing the mandrel 336 longitudinally within the bore and forcing themandrel 336 through the tube 200. Additionally, in some embodimentsmultiple sets of track assemblies or rollers may be used tosimultaneously advance a pushrod toward a tube and advance the tubetoward the pushrod.

Although the systems and methods described above include a variety ofgrippers that can secure tubes for swage autofrettage, the systems andmethods of the present technology can include the use of a variety ofother devices or components that can secure tubes for swageautofrettage. For example, in several embodiments a gripper can includea threaded receiver. In such embodiments, the tube 200 can includeexternal threads that can engage with internal threads in the threadedreceiver. In operation, the tube 200 can be rotated to releasably engagewith the threaded receiver, and the threaded receiver can secure thetube 200 in a fixed position during swage autofrettage.

FIG. 9 is a perspective view of a waterjet system 900 having tubes 200configured in accordance with an embodiment of the disclosure. Thewaterjet system 900 includes a fluid-pressurizing device 902 (shownschematically) configured to pressurize a process fluid (e.g., water) toa pressure suitable for waterjet processing. In some embodiments, thefluid-pressurizing device 902 can include a multiplex pump system thatis at least generally similar to pump systems described in U.S. patentapplication Ser. No. 14/624,374, filed Feb. 17, 2015, and entitled“MULTIPLEX PUMP SYSTEMS AND ASSOCIATED METHODS OF USE WITH WATERJETSYSTEMS AND OTHER HIGH PRESSURE FLUID SYSTEMS,” the entirety of which isincorporated by reference herein. The waterjet system 900 can furtherinclude a waterjet assembly 904 operably connected to thefluid-pressurizing device 902 via one or more tubes 200 extendingbetween the fluid pressurizing device 902 and the waterjet assembly 904.In the illustrated embodiment, the tubes 200 are also connected in fluidcommunication to a safety valve 932 and a relief valve 934.

The waterjet assembly 904 can include a cutting head 911 downstream fromthe pressurizing device 902 and having a jet outlet 908 and a controlvalve 910. The waterjet system 900 can further include a user interface916 supported by a base 914, and an abrasive-delivery apparatus 920configured to feed particulate abrasive material from an abrasivematerial source 921 to the waterjet assembly 904. The system 900 canalso include a controller 924 (shown schematically) that is operablyconnected to a user interface 916. The controller 924 can include aprocessor 928 and memory 930 and can be programmed with instructions(e.g., non-transitory instructions contained on a computer-readablemedium) that, when executed, control operation of the system 900. Inoperation, the system 900 can perform cutting operations via a waterjetformed via ultrahigh pressure liquid delivered by the tubes 200. Theincreased fatigue life of the tubes 200 (as described above) cansignificantly improve the performance of the system 900 by enablingadditional pressurization cycles, reducing maintenance requirements, andreducing operational costs.

Systems and devices configured in accordance with the present disclosurecan provide several advantages over prior systems for performingautofrettage. For example, the systems 300, 400 and 500, can performswage autofrettage on components that would be too long for traditionalswage autofrettage, and that would only be amenable to hydraulicautofrettage. Specifically, prior systems for swage autofrettage utilizehydraulic presses or other components that push on a pushrod at an endof the pushrod that is opposite to the end that exerts a force on amandrel. Accordingly, in these prior systems, the full length of thepushrod is under compressive stress and unsupported prior to enteringthe component. In contrast to these devices, the track assemblies 306,the rollers 406 and the pusher 502 drive a pushrod from a positionadjacent to the tube 200, thereby reducing the portion of the pushrodthat is both subject to compressive stress and unsupported by the tube200. In several embodiments, for example, the first grippers 316 and 416can be positioned less than 6 inches from the tracks 312 or the rollers406. Similarly, the first gripper 506 a can be positioned less than 6inches from the pusher 512. Accordingly, the unsupported position of thepushrod can be less than 6 inches. In other embodiments, the distancesbetween the gripping assemblies and the tracks or rollers (or betweenthe first gripper and the pusher) can be greater than or less than 6inches. Importantly though, the systems disclosed herein can reduce theunsupported portion of the pushrod, independent of the pushrod's length.Accordingly, the disclosed systems and methods can perform swageautofrettage on components of significantly longer lengths.

In the embodiment of FIG. 5, a distal portion 337 of the pushrod 311 ispositioned adjacent the third gripper 506 c and the second gripper 506b, while a proximal portion of the tube 200 is positioned adjacent thefirst gripper 506 a. In several embodiments, the third gripper 506 c andthe second gripper 506 b can be positioned to engage the pushrod 311within a distalmost third portion of the pushrod 311, and the firstgripper 506 a can be positioned to engage the tube 200 within aproximalmost third portion of the tube 200.

In addition to reducing the compressive loads on pushrods, thecontinuous feeding of pushrods by the track assemblies 306, the rollers406 and the pusher 502 provides for the use of tubes and pushrods havingsignificantly longer lengths. That is, prior systems utilizing hydraulicpresses or other devices do not have a stroke that is long enough topush a mandrel through long tubes, and therefore require the use of oneor more additional push rods. The continuous feeding of pushrodsprovided by the systems disclosed herein overcome this limitation.

Furthermore, the systems 300 and 400 can perform swage autofrettage onlong tubes or other components in an uninterrupted manner. That is, thesystems 300 and 400 can drive a mandrel through a long tube at aconstant speed. In some embodiments, the constant speed can reducevariations in the residual stresses that are induced in the tubes,thereby producing more uniform and stronger tubes. Additionally, in someembodiments, the speed can be controlled to enhance the effects of theautofrettage. For example, tubes having different alloy compositions ordifferent dimensions may benefit from particular speeds.

As discussed above, in some embodiments, the control panels 326 may beused to activate several components to perform the swage autofrettage.For example, in some embodiments, an operator can utilize the controlpanels of the systems 300, 400 and 500 to perform one or more steps ofthe methods 600, 700 and 800, respectively.

Furthermore, embodiments configured in accordance with the presentdisclosure can include additional components or devices to fullyautomate the swage autofrettage of tubes. In one example, conveyors,robotic arms and/or other assembly line or manufacturing devices may beused to sequentially load tubes, mandrels, pushrods, or other componentsand automatically push one or more mandrels through a series of tubes.

From the foregoing, it will be appreciated that specific embodimentshave been described herein for purposes of illustration, but thatvarious modifications may be made without deviating from the spirit andscope of the present disclosure. Those skilled in the art will recognizethat numerous modifications or alterations can be made to the componentsor systems disclosed herein. For example, in several embodiments, ratherthan utilizing a mandrel separate from a pushrod, a mandrel can be anintegral part of a pushrod. Moreover, certain aspects of the presentdisclosure described in the context of particular embodiments may becombined or eliminated in other embodiments. Further, while advantagesassociated with certain embodiments have been described in the contextof those embodiments, other embodiments may also exhibit suchadvantages, and not all embodiments need necessarily exhibit suchadvantages to fall within the scope of the present disclosure.Accordingly, the inventions are not limited except as by the appendedclaims.

We claim:
 1. A method of performing swage autofrettage on a pressurevessel, the pressure vessel consisting of a single-piece elongate metaltube, the method comprising: longitudinally aligning an elongatepushrod, a mandrel, and the single-piece elongate metal tube having alongitudinal bore and an annular wall extending around the bore, whereina ratio of a length of the elongate metal tube to an inside diameter ofthe elongate metal tube is at least 90, and wherein the mandrel iseither separate from the pushrod or part of the pushrod; gripping aportion of a side surface of the tube; gripping a portion of a sidesurface of the pushrod; and decreasing a distance between the portion ofthe side surface of the tube and the portion of the side surface of thepushrod to advance the mandrel distally within the bore, therebyexpanding an inner diameter of the bore without expanding an outerdiameter of the tube, inducing residual longitudinal and tangentialcompressive stress at an inner portion of the wall, and inducingresidual longitudinal and tangential tensile stress at an outer portionof the wall.
 2. The method of claim 1 wherein decreasing the distancebetween the portion of the side surface of the tube and the portion ofthe side surface of the pushrod includes applying traction to the sidesurface of the pushrod to feed the pushrod into the bore.
 3. The methodof claim 1 wherein decreasing the distance between the portion of theside surface of the tube and the portion of the side surface of thepushrod includes applying traction to the side surface of the tube tofeed the tube over the pushrod.
 4. The method of claim 1 whereindecreasing the distance between the portion of the side surface of thetube and the portion of the side surface of the pushrod includessimultaneously applying traction to the side surface of the tube andapplying traction to the side surface of the pushrod to simultaneouslyfeed the pushrod into the bore and feed the tube over the pushrod. 5.The method of claim 1 wherein: gripping the portion of the side surfaceof the pushrod includes contacting an outwardly facing surface of a beltand the portion of the side surface of the tube; and gripping theportion of the side surface of the pushrod while moving the belt along alooped path decreases the distance between the portion of the sidesurface of the tube and the portion of the side surface of the pushrod.6. The method of claim 1 wherein: gripping the portion of the sidesurface of the pushrod includes contacting an outwardly facing surfaceof a roller and the portion of the side surface of the tube; andgripping the portion of the side surface of the pushrod while rotatingthe roller decreases the distance between the portion of the sidesurface of the tube and the portion of the side surface of the pushrod.7. The method of claim 1 wherein gripping the portion of the sidesurface of the pushrod includes gripping the portion of the side surfaceof the pushrod at a distalmost third of a length of the pushrod outsidethe bore.
 8. The method of claim 1 wherein: the bore has an innerdiameter less than 0.2 inch; and decreasing the distance between theportion of the side surface of the tube and the portion of the sidesurface of the pushrod includes decreasing the distance between theportion of the side surface of the tube and the portion of the sidesurface of the pushrod by at least three feet.
 9. The method of claim 1wherein: the bore has an inner diameter less than 0.25 inch; anddecreasing the distance between the portion of the side surface of thetube and the portion of the side surface of the pushrod includesdecreasing the distance between the portion of the side surface of thetube and the portion of the side surface of the pushrod by at least fivefeet.
 10. The method of claim 1 wherein gripping the portion of the sidesurface of the tube includes clamping the portion of the side surface ofthe tube to secure the tube in a fixed position.
 11. A method ofperforming swage autofrettage on a pressure vessel, the pressure vesselconsisting of a single-piece elongate metal tube, the method comprising:advancing a mandrel distally within a bore of the single-piece elongatetube by at least one of feeding an elongate pushrod into the bore orfeeding the tube over the pushrod, wherein the mandrel is eitherseparate from the pushrod or part of the pushrod, and wherein theelongate tube has an aspect ratio of a length of the elongate tube to aninner diameter of the elongate tube of at least 90; and longitudinallyand radially dislocating first metal microstructures at an inner portionof a wall of the tube without longitudinally and radially dislocatingsecond metal microstructures at an outer portion of the wall.
 12. Themethod of claim 1 wherein longitudinally and radially dislocating thefirst metal microstructures includes longitudinally and radiallydislocating the first metal microstructures throughout a full length ofthe tube.
 13. The method of claim 1, further comprising: inducingresidual longitudinal and tangential compressive stress at the innerportion of the wall; and inducing residual longitudinal and tangentialtensile stress at the outer portion of the wall.
 14. The method of claim1, further comprising: inducing residual longitudinal and tangentialcompressive stress at the inner portion of the wall substantiallyuniformly throughout a full length of the tube; and inducing residuallongitudinal and tangential tensile stress at the outer portion of thewall substantially uniformly throughout the full length of the tube. 15.The method of claim 1, further comprising: gripping a portion of a sidesurface of the tube; and gripping a portion of a side surface of thepushrod, wherein advancing the mandrel distally within the bore includesadvancing the mandrel distally within the bore by decreasing a distancebetween the portion of the side surface of the tube and the portion ofthe side surface of the pushrod.
 16. The method of claim 15 wherein:gripping the portion of the side surface of the pushrod includescontacting an outwardly facing surface of a belt and the portion of theside surface of the tube; and decreasing the distance between theportion of the side surface of the tube and the portion of the sidesurface of the pushrod includes moving the belt along a looped path. 17.The method of claim 15 wherein: gripping the portion of the side surfaceof the pushrod includes contacting an outwardly facing surface of aroller and the portion of the side surface of the tube; and decreasingthe distance between the portion of the side surface of the tube and theportion of the side surface of the pushrod includes rotating the roller.18. The method of claim 15 wherein gripping the portion of the sidesurface of the pushrod includes gripping the portion of the side surfaceof the pushrod at a distalmost third portion of the pushrod outside thebore.
 19. The method of claim 15 wherein: the bore has an inner diameterless than 0.2 inch; and decreasing the distance between the portion ofthe side surface of the tube and the portion of the side surface of thepushrod includes decreasing the distance between the portion of the sidesurface of the tube and the portion of the side surface of the pushrodby at least three feet.
 20. The method of claim 15 wherein: the bore hasan inner diameter less than 0.25 inch; and decreasing the distancebetween the portion of the side surface of the tube and the portion ofthe side surface of the pushrod includes decreasing the distance betweenthe portion of the side surface of the tube and the portion of the sidesurface of the pushrod by at least five feet.
 21. The method of claim 1wherein the tube is configured to convey liquid having at pressures fromatmosphere up to 60,000 psi.
 22. The method of claim 1, wherein the tubeis configured to withstand pressurization cycles from atmosphericpressure to 60,000 psi.
 23. The method of claim 11 wherein the tube isconfigured to convey liquid having at pressures from atmosphere up to60,000 psi.
 24. The method of claim 11, wherein the tube is configuredto withstand pressurization cycles from atmospheric pressure to 60,000psi.